% File src/library/graphics/man/bxp.Rd
% Part of the R package, https://www.R-project.org
% Copyright 1995-2026 R Core Team
% Distributed under GPL 2 or later

\name{bxp}
\alias{bxp}
\title{Draw Box Plots from Summaries}
\description{
  \code{bxp} draws box plots based on the given summaries in \code{z}.
  It is usually called from within \code{\link{boxplot}}, but can be
  invoked directly.
}
\usage{
bxp(z, notch = FALSE, width = NULL, varwidth = FALSE,
    outline = TRUE, notch.frac = 0.5, log = "",
    border = par("fg"), pars = NULL, frame.plot = axes,
    horizontal = FALSE, ann = TRUE,
    add = FALSE, at = NULL, show.names = NULL,
    panel.first = NULL, panel.last = NULL, \dots)
}
\arguments{
  \item{z}{a list containing data summaries to be used in constructing
    the plots.  These are usually the result of a call to
    \code{\link{boxplot}}, but can be generated in any fashion.}
  \item{notch}{if \code{notch} is \code{TRUE}, a notch is drawn in each
    side of the boxes.  If the notches of two plots do not overlap then
    the medians are significantly different at the 5 percent level.}
  \item{width}{a vector giving the relative widths of the boxes making
    up the plot.}
  \item{varwidth}{if \code{varwidth} is \code{TRUE}, the boxes are drawn
    with widths proportional to the square-roots of the number of
    observations in the groups.}
  \item{outline}{if \code{outline} is not true, the outliers are not
    drawn.}
  \item{notch.frac}{numeric in (0,1). When \code{notch = TRUE}, the
    fraction of the box width that the notches should use.}
  \item{border}{character or numeric (vector), the color of the box
    borders.  Is recycled for multiple boxes.  Is used as default for
    the \code{boxcol}, \code{medcol}, \code{whiskcol}, \code{staplecol},
    and \code{outcol} options (see below).
  }
  \item{log}{character, indicating if any axis should be drawn in
    logarithmic scale, as in \code{\link{plot.default}}.}
  \item{frame.plot}{logical, indicating if a \sQuote{frame}
    (\code{\link{box}}) should be drawn; defaults to \code{TRUE}, unless
    \code{axes = FALSE} is specified.}
  \item{horizontal}{logical indicating if the  boxplots should be
    horizontal; default \code{FALSE} means vertical boxes. See \sQuote{Note}.}
  \item{ann}{a logical value indicating whether the default annotation
    (title and x and y axis labels) should appear on the plot.}
  \item{add}{logical, if true \emph{add} boxplot to current plot.}
  \item{at}{numeric vector giving the locations where the boxplots
    should be drawn, particularly when \code{add = TRUE}; defaults to
    \code{1:n} where \code{n} is the number of boxes.}
  \item{show.names}{Set to \code{TRUE} or \code{FALSE} to override the
    defaults on whether an x-axis label is printed for each group.}
  \item{panel.first}{a \sQuote{function} (not an \sQuote{expression}!) 
    that is called without arguments after the plot axes are set up 
    but before any plotting takes place. This can
    be useful for drawing background grids.}
  \item{panel.last}{a \sQuote{function} (not an \sQuote{expression}!) 
    that is called after plotting has taken place but before the 
    axes and title are added.}
  \item{pars,\dots}{\link{graphical parameters} (etc) can be passed as
    arguments to this function, either as a list (\code{pars}) or
    normally(\code{\dots}), see the following.  (Those in \code{\dots}
    take precedence over those in \code{pars}.)

    \code{xaxt}, \code{yaxt}, \code{las}, \code{cex.axis},
    \code{gap.axis}, and
    \code{col.axis} are passed to \code{\link{axis}}, and \code{main},
    \code{cex.main}, \code{col.main}, \code{sub}, \code{cex.sub},
    \code{col.sub}, \code{xlab}, \code{ylab}, \code{cex.lab}, and
    \code{col.lab} are passed to \code{\link{title}}.

    In addition, \code{axes} is accepted (see
    \code{\link{plot.window}}), with default \code{TRUE}.

    The following arguments (or \code{pars} components) allow further
    customization of the boxplot graphics.  Their defaults are typically
    determined from the non-prefixed version (e.g., \code{boxlty} from
    \code{lty}), either from the specified argument or \code{pars}
    component or the corresponding \code{\link{par}} one.
    \describe{
      \item{boxwex:}{a scale factor to be applied to all boxes.  When there
        are only a few groups, the appearance of the plot can be improved by
        making the boxes narrower.  The default depends on \code{at} and
        typically is \eqn{0.8}.}
      \item{staplewex, outwex:}{staple and outlier line width expansion,
        proportional to box width; both default to 0.5.}
      \item{boxlty, boxlwd, boxcol, boxfill:}{box outline type, width,
        color, and fill color (which currently defaults to \code{col} and will
        in future default to \code{par("bg")}).}
      \item{medlty, medlwd, medpch, medcex, medcol, medbg:}{median line type,
        line width, point character, point size expansion, color, and
        background color.  The default \code{medpch = NA} suppresses the
        point, and \code{medlty = "blank"} does so for the line.
        Note that \code{medlwd} defaults to
        \eqn{3\times}{3x} the default \code{lwd}.}
      \item{whisklty, whisklwd, whiskcol:}{whisker line type (default:
        \code{"dashed"}), width, and color.}
      \item{staplelty, staplelwd, staplecol:}{staple (= end of whisker) line
        type, width, and color.}
      \item{outlty, outlwd, outpch, outcex, outcol, outbg:}{outlier line
        type, line width, point character, point size expansion, color, and
        background color.  The default \code{outlty =  "blank"} suppresses the
        lines and \code{outpch = NA} suppresses points.}
    }
  }%.../pars
}
\note{
  When \code{add = FALSE}, \code{xlim} now defaults to \code{xlim =
    range(at, *) + c(-0.5, 0.5)}.  It will usually be a good idea to
  specify \code{xlim} if the "x" axis has a log scale or \code{width} is
  far from uniform.

  If \code{horizontal = TRUE}, the "y" axis is the horizontal axis and the
  "x" axis is the vertical axis.  Graphical parameters \code{xlim/ylim} and
  \code{xaxs/yaxs} are reversed in this case.  Other axis related parameters
  treat the vertical axis as "y" and the horizontal axis as "x".
}
\value{
  An invisible vector, actually identical to the \code{at} argument,
  with the coordinates ("x" if horizontal is false, "y" otherwise) of
  box centers, useful for adding to the plot.
}
\author{
  The R Core development team and Arni Magnusson
  (then at U Washington) who has provided most changes for the
  box*, med*, whisk*, staple*, and out* arguments.
}
\references{
  \bibshow{R:Becker+Chambers+Wilks:1988}
}
\examples{
require(stats)
set.seed(753)
(bx.p <- boxplot(split(rt(100, 4), gl(5, 20))))
op <- par(mfrow =  c(2, 2))
bxp(bx.p, xaxt = "n")
bxp(bx.p, notch = TRUE, axes = FALSE, pch = 4, boxfill = 1:5)
bxp(bx.p, notch = TRUE, boxfill = "lightblue", frame.plot = FALSE,
    outline = FALSE, main = "bxp(*, frame.plot= FALSE, outline= FALSE)")
bxp(bx.p, notch = TRUE, boxfill = "lightblue", border = 2:6,
    ylim = c(-4,4), pch = 22, bg = "green", log = "x",
    main = "... log = 'x', ylim = *")
par(op)
op <- par(mfrow = c(1, 2))

## single group -- no label
boxplot (weight ~ group, data = PlantGrowth, subset = group == "ctrl")
## with label
bx <- boxplot(weight ~ group, data = PlantGrowth,
              subset = group == "ctrl", plot = FALSE)
bxp(bx, show.names=TRUE)
par(op)

## passing gap.axis=* to axis(), PR#18109:
boxplot(matrix(100*rnorm(1e3), 50, 20),
        cex.axis = 1.5, gap.axis = -1)# showing *all* labels

%% examples for new (S+ like) features
z <- split(rnorm(1000), rpois(1000, 2.2))
boxplot(z, whisklty = 3, main = "boxplot(z, whisklty = 3)")

## Colour support similar to plot.default:
op <- par(mfrow = 1:2, bg = "light gray", fg = "midnight blue")
boxplot(z,   col.axis = "skyblue3", main = "boxplot(*, col.axis=..,main=..)")
plot(z[[1]], col.axis = "skyblue3", main =    "plot(*, col.axis=..,main=..)")
mtext("par(bg=\"light gray\", fg=\"midnight blue\")",
      outer = TRUE, line = -1.2)
par(op)

## Mimic S-Plus:
splus <- list(boxwex = 0.4, staplewex = 1, outwex = 1, boxfill = "grey40",
              medlwd = 3, medcol = "white", whisklty = 3, outlty = 1, outpch = NA)
boxplot(z, pars = splus)
## Recycled and "sweeping" parameters
op <- par(mfrow = c(1,2))
 boxplot(z, border = 1:5, lty = 3, medlty = 1, medlwd = 2.5)
 boxplot(z, boxfill = 1:3, pch = 1:5, lwd = 1.5, medcol = "white")
par(op)
## too many possibilities
boxplot(z, boxfill = "light gray", outpch = 21:25, outlty = 2,
        bg = "pink", lwd = 2,
        medcol = "dark blue", medcex = 2, medpch = 20)
}
\keyword{aplot}
